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Biochemistry Chapters 1-3 Study Cards

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Each of the following is a noncovalent interaction EXCEPT
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A) a hydrogen bond. B) a carbon-hydrogen bond. C) the interaction between an amino and a carboxylate group. D) a van der Waals interaction. E) an interaction between —NH3+ and a water molecule. Answer: B
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The most important noncovalent interaction in biochemistry is the ________ bond.
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Hydrogen
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Which of the following is FALSE when considering van der Waals interactions?
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A) The van der Waals radius represents the most stable distance between two interacting centers. B) Van der Waals radii can determine molecular surfaces. C) Molecules that interact by van der Waals forces do not interpenetrate. D) The total interaction energy is the sum of the attractive and repulsive forces. E) They are not important in determining the stability of three-dimensional structures of proteins. Answer: E
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Which of the following in biological compounds are sufficiently electronegative to serve as strong donors in a hydrogen bond?
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A) Hydrogen and oxygen B) Oxygen and nitrogen C) Nitrogen and hydrogen D) Hydrogen and carbon E) Nitrogen and carbon Answer: B
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Hydrogen bonds share features of both covalent and noncovalent bonds.
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TRUE
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Which of the following is TRUE of hydrophobic molecules?
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A) They have limited solubility in water. B) Water forms a cage-like structure around them. C) Dissolving in water decreases the entropy of the mixture. D) They self-associate by releasing some of the surrounding water molecules. E) All of the above Answer: E
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Water is both a hydrogen bond donor and acceptor.
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TRUE
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Amphipathic molecules are not able to interact via van der Waals forces.
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FALSE
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Ionic compounds can be readily dissolved in water because the high dielectric constant of water screens and decreases the ________ force between the oppositely charged ions.
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Electrostatic
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The ________ describes the tendency for hydrophobic molecules to aggregate because of the exclusion of water with the consequent increase of entropy of the solvent.
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Hydrophobic Effect
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Glycine cannot serve as a buffer because it has two ionizable groups.
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FALSE
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The average charge on an amino acid below its pI will be positive.
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TRUE
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Calculate the acid dissociation constant Ka of a 0.2 M solution of weak acid that is 0.1% ionized.
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Answer: 2 × 10-7
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Calculate the pH of a 0.1 M phosphate buffer (pKa = 6.86) that contains equal amounts of acid and conjugate base.
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6.86
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Calculate the pH of a 0.2 M acetate buffer (pKa = 4.77) that contains twice as much acid as conjugate base.
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4.47
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The pKa of each amino acid residue in a protein will not be influenced by the adjacent residue.
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FALSE
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Calculate the pH at the end of an enzyme-catalyzed reaction if it were carried out in a 0.1 M phosphate buffer, pH 6.86 and 0.005 M of acid was produced during the reaction?
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6.77
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If hydroxide is added to an amino acid it will become increasingly ________ charged.
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Negatively
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Calculate the pH of a weak acid that is 0.2% ionized in a 0.2 M solution.
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3.39
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The net charge on an amino acid at its isoelectric point (pI) is ________.
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Zero
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Many proteins interact with DNA at physiological pH because:
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A) proteins are naturally attracted to DNA regardless of the pH. B) the negatively charged DNA is electrostatically attracted to positively charged regions on proteins. C) the positively charged DNA is electrostatically attracted to negatively charged regions on proteins. D) proteins and DNA interact using mainly hydrophobic interactions. E) both proteins and DNA are at their isoelectric points at physiological pH and tend to aggregate. Answer: B
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Small ions in biological fluids:
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A) encourage strong electrostatic interactions between oppositely charged macroions at low ionic strengths. B) encourage strong electrostatic interactions between oppositely charged macroions at high ionic strengths. C) have no effect on the interactions between oppositely charged macroions. D) tend to cluster around macroions of the same charge. E) have large effects on pH. Answer: A
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The water content in the human body is approximately
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70%
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The Four most abundant chemical elements in living systems are:
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Hydrogen, Carbon, Nitrogen and Oxygen
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Nearly all proteins contain
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Sulfur
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Which of the following statements is FALSE?
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Proteins are the only biological polymer that can catalyze biochemical reactions
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Which of the following is NOT classed as a lipid?
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Glycerol
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Amino acids and simple organic compounds like carbon dioxide and hydrogen cyanide cannot be produced without the use of enzymes
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False
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Oxidation reduction reactions, which are the basis of many biochemical reactions and pathways, cannot take place in the absence of oxygen
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False
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Many biochemical reactions that form biopolymers from monomeric units involve the removal of water
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True
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The principle component of a biological membrane is a triglyceride
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False
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The chemical element __________ has a role in both transfer of energy as well as in the structure of nucleic acids
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Phosphorus
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List the four major classes of biological macromolecules.
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Lipids, Carbohydrates, Proteins and Nucleic Acids
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An amphiatic molecule provides the foundation for biological membranes because they have both ____ and ____ functions
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Hydrophobic and Hydrophilic
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Genomics is concerned with the entire _____, while ______ is focused on identifying all of the proteins of a cell
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Genome, proteomics
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Which of the following statements is FALSE?
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Organisms are open systems as they can create energy from their environments
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Which of the following statements is FALSE?
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Biological systems are highly ordered so entropy changes are not relevant
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A biochemical reaction will proceed in the direction as written if:
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G < 0
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Life is an irreversible process, such that it never comes to equilibrium
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True
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The equilibrium constant of a reaction:
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Is related to the change in free energy of the reaction
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The change in enthalpy (?H) for the complete oxidation of a fatty acid is different depending on whether it occurs via a biochemical path combustion to CO2 and H2O
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False
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A reaction at its lowest energy state for the system and with equal rates in the forward and reverse directions is said to be at _______
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Equilibrium
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A reaction at equilibrium can be driven in one direction or the other by changing the ______ of reactants or products
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Concentration
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A thermodynamically unfavorable reaction can become favorable if the mass action ratio is _________ than the equilibrium mass action ratio
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Less
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Calculate the equilibrium constant for the enzymatic hydrolysis of 0.1 M glucose-6-phosphate to glucose and inorganic phosphate given 0.05% of the original glucose-6-phosphate remained after reaching equilibrium and the activity of water is unity
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199.8
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The ?Go of a reaction:
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Can be used to calculate whether a reaction is thermodynamically favorable under defined non-standard conditions
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Calculate the ?G?’ for the reaction Fructose-6-phosphate ? glucose-6-phosphate Given the equilibrium constant is 1.97 and the physiological relevant temperature is 37 C
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-1.75 kj/mol
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A thermodynamically unfavorable reaction can become favorable when coupled to a highly endergonic reaction
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False
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A reaction with a large negative free energy of hydrolysis can be coupled to the synthesis of ATP from ADP and Pi
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True
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In a general redox reaction, the reductant becomes oxidized and the oxidant becomes reduced
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True
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The standard reduction potential is a measure of the ability of a reductant to _____ an electron
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Lose